Add a temp variable to ff_sine_window_init() to match the way wma.c computed

window before r14757. This fixes a regression introduced by r14757 on amd64.

Originally committed as revision 14982 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/mdct.c

@@ -59,9 +59,10 @@ float *ff_sine_windows[5] = {
 
 // Generate a sine window.
 void ff_sine_window_init(float *window, int n) {
+    float alpha = M_PI / (2.0 * n);
     int i;
     for(i = 0; i < n; i++)
-        window[i] = sin((i + 0.5) / (2 * n) * M_PI);
+        window[i] = sin((i + 0.5) * alpha);
 }
 
 /**